Kingdom Fungi
Saprobes are decomposers that break down organic matter, while others are parasitic fungi that prey on their own kind, consuming other fungi and controlling population in the soil. These fun guys come in handy when a disease-carrying fungus is attacking a plant!
or symbiotic (e.g., mycorrhiza, lichens).
Reproduction: via spores, released sexually or asexually.
Major Phyla: The most significant groups are Ascomycota (sac fungi, e.g., Penicillium), Basidiomycota (club fungi, e.g., mushrooms), Zygomycota (bread moulds), and Chytridiomycota.
Ecological Role: They are vital for nutrient cycling and decomposition, though some cause diseases in plants and animals.
Mycorrhizae:
This group of fungi have a symbiotic relationship with plants, in which the fungi provide valuable nutrients in exchange for processed sugar from the plant!
In the insect world, fungi act as both prey and predator. Fungi are a wonderful food source for many insects, and the opposite is true as well! Entomopathogenic fungi use insects as both a food source and a vessel for dispersing their offspring.
One last group of predacious fungi are the those that prey on their own kind, consuming other fungi and controlling population in the soil. These fun guys come in handy when a disease-carrying fungus is attacking a plant!
Soil Bacteria:
Rhizobia (leguminous plants) - Convert N2 gas into NH4
Rhizobia are soil bacteria that fix nitrogen after becoming established inside the root nodules of legumes. Rhizobia require a plant host; they cannot independently fix nitrogen. These bacteria have an intimate relationship with leguminous roots, turning N2(Nitrogen Gas) into NH4(Ammonium) for improving soil pH.
Actinobacteria
Actinobacteria are a very interesting group of microorganisms indeed! At first glance these chains of bacteria look strikingly similar to a fungal strand, but genetic analysis of actinobacteria has revealed that they are actually prokaryotes containing no bound nucleus versus the eukaryotic fungi!
Actinobacteria are the agents responsible for the rich aroma of healthy soil. While about 90 percent of plants maintain a symbiotic relationship with fungi called Mycorrhizae, about ten percent of plants enter into a different sort of relationship with Actinobacteria. Actinobacteria produce certain compounds that act as soil fumigants on fungi, impeding the development of any mycorrhizal relation or parasitic predation towards the plant. This allows actinobacteria to work with the plant and greatly improve its immunity.
Microaggregates and Macroaggregates
Glues for Hyphae structures
The massive diversity of soil biology contains thousands upon thousands of small groups of bacteria, called Microaggregates. These small clusters of bacteria excrete materials that act as glue, sticking to fungal hyphae and building large living structures called Macroaggregates. The grouping of these bacteria and fungi helps to form soil structure, giving it shape and retaining nutrients that can be utilized and extracted by the biology living within it.
Micro and Macro-Arthropods
Many bugs, known as arthropods, make their home in the soil. Nearly every soil is home to many different arthropod species. Certain row-crop soils contain several dozen species of arthropods in a square mile. Several thousand different species may live in a square mile of forest soil.
Shredders
The majority of Macro (large) Arthropods can be considered shredders. Extremely useful as they are in the ecosystem, Shredders chew up dead plant matter as they eat bacteria and fungi on the surface of the plant matter. By doing this, they take in and excrete valuable soil nutrients and become vessels for entomopathogenic fungi as well as certain stored resources.
By breaking down the larger pieces of decomposing material on the soil surface, Shredders make decomposition short work for bacteria and fungus within the soil, while also stimulating the growth of microbial and bacterial populations.
Predators
Predators and macropredators can be either generalists, feeding on many different prey types, or specialists, hunting only a single prey type. Predators include centipedes, spiders, ground-beetles, scorpions, skunk-spiders, pseudoscorpions, ants, and some mites. Many predators eat crop pests, and some, such as beetles and parasitic wasps, have been developed for use as commercial biocontrols.
Amoeba
Soil amoebae roam the film of water coating each soil particle. This water layer is so thin that an amoeba can survive in very dry soils. An amoeba uses its blobby tentacles both to move and to feed. Amoebae eat so many bacteria that they compete with nematodes for food, controlling nematode populations.
Amoebae belong to the soil recycling crew. They can't use all of the nutrients in the bacteria they eat. So a lot of the nutrients go back into the soil. Amoebae and other protozoa must breathe oxygen, so they mostly live in the most aerated layers of soils.
Flagellates
Flagellates are a type of aerobic protozoan that consume bacteria within the soil. Flagellates do the job of immobilizing and mobilizing nutrients, making them available for plants to use.
Once bacteria are consumed, their nutrients are held within the Flagellates' structure until excretion, manipulation, or consumption of the flagellate occurs. If Flagellates weren't there to process nutrients, a lot of what our plants need to grow would never become available in the soil!
Ciliates
These protists are typically seen quite easily through a standard light microscope because of their size and fluid movement patterns. Their voracious appetites dine on detritus material like minerals, plant material, etc. that can be then solubilized through the ciliate’s digestion into a plant available food. They have a multitude of sizes, shapes, and behaviours. Some have tails that are used to attach onto objects while others have giant(at a magnification of 400x) spikes sticking out of different parts of their body.
Typically, when we see ciliates, we know that we are not getting adequate oxygen for our roots to thrive. If ciliate numbers are too high, then they are most likely to be outcompeting many of the other organisms necessary for healthy soil ecology.
Nematodes are non-segmented worms typically 1/500 of an inch (50 µm) in diameter and 1/20 of an inch (1 mm) in length. Those few species responsible for plant diseases have received a lot of attention, but far less is known about the majority of the nematode community that plays beneficial roles in soil.
An incredible variety of nematodes function at several trophic levels of the soil food web. Some feed on the plants and algae (first trophic level); others are grazers that feed on bacteria and fungi (second trophic level); and some feed on other nematodes (higher trophic levels).
Free-living nematodes can be divided into four broad groups based on their diet.
Bacterial Feeding Nematodes
This bacterial-feeding nematode releases plant-available nitrogen when they consume bacteria. These Nematodes typically dwell near plant roots, where bacteria tend to congregate. In digesting bacteria, Nematodes also fix nitrogen, converting the ingested nitrogen into ammonium. The action of grazing on bacteria also stimulates bacterial growth, effectively keeping levels of bacterial biology within the soil in check.
Fungal-feeding nematodes have small, narrow stylets, or spears, in their stoma (mouth) which they use to puncture the cell walls of fungal hyphae and withdraw the cell fluid. This interaction releases plant-available nitrogen from fungal biomass. They also benefit plants by consuming potentially pathogenic fungi, converting them to safe and useful plant nutrients.
Predatory Nematodes eat all types of nematodes and protozoa. They eat smaller organisms whole, or attach themselves to the cuticle of larger nematodes, scraping away until the prey’s internal body parts can be extracted. These predatory nematodes are highly useful in controlling the populations of bacterial and fungal feeding nematodes, acting as a bio-control agent monitoring fungal and bacterial populations through grazing. This sort of tiered regulation is vital to maintaining effective and healthy soil ecology.
Omnivorous Nematodes eat a variety of organisms or may have a different diet at each life stage. Root-feeders are plant parasites and thus are not free-living in the soil. These nematodes serve a variety of functions, both beneficial and potentially dangerous. Many root-feeding nematodes carry pathogens that can cause disease in plants, but in a healthy soil ecology they are effective food sources and vehicles for spreading microbes and bacteria.